You can order parts directly from Bradley. Just call their customer service, but I would suspect you will blow the fuse again.
Did the inline fuse fail immediately? How hot did the cabinet get before you noticed the element not working? I see you have a PID. My feeling is, if you can have redundant systems, then that is better than one. I've seen more than one post, in which the PID has failed during operation.
I've noticed some confusion about the inline fuse that are in the Bradley. I believe the in-line fuse in the Bradley is an electrical fuse, and not a mechanical one which works by heat. But I'm not absolutely sure.
If it is electrical, and the stock wiring of the Bradley is 14ga, the inline fuse will have a 16ga wire in it, so if too many amps/voltage is flowing through the wire, that the fuse will blow before any damage can occur to other components. Adding an 1100 watt element (in addition to the fan), even though you increased the wire size, the inline fuse is the same, and it can't carry the increase load. Again; if it is an electrical fuse, it would be better to look for a fuse that is designed to carry the load of an 1100 watt element, that is consistent to your upgraded wiring.
If the inline fuse is a mechanical fuse, then it is worth installing a new one, and make sure you set your PID no higher that 250°F - 275°F.